An aqueous ink suitable for a ball-point pen and an ink-jet recording should have adequate stability with time, discharging properties, lubricating ability, water-resistance and light resistance, in addition to good writing and recording properties and good fixing properties of the written or recorded images. Conventional aqueous ink, however, has poor stability with time and lubricating properties, which often cause plugging of the pen tip and nozzle. In the case of a ball-point pen, the rotation of the ball is obstructed and a ball holder is worn resulting in a bad feeling during writing. In the case of ink-jet recording, the plugging inhibits discharging of the ink necessary to make the recorded letters and images distinct.
In order to obviate the above mentioned problems, many improvements have been done, for example, an aqueous ink containing a polyalkylene glycol derivative (Japanese Kokai Publication (unexamined) 65608/1979), an aqueous ink containing an unsaturated fatty acid (Japanese Patent Publication (examined) 3718/1982), an aqueous ink containing a phosphoric acid derivative (Japanese Kokai Publication (unexamined) 5773/1982 and 28472/1985) and an aqueous ink containing a polyoxyethylene fatty acid ester or a polyoxyethylene higher alcohol ether (Japanese Kokai Publication (unexamined) 143602/1975.
These inks try to improve the defects by formulating therein a modifying agent, such as a lubricating agent, a wetting agent or a water-resisting agent. The modifying agent is an improvement to a certain extent, but the obtained inks still necessitate some improvements.